// The MIT License (MIT)
//
// Copyright (c) Itay Grudev 2015 - 2018
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.

#ifndef SINGLE_APPLICATION_H
#define SINGLE_APPLICATION_H

#include <QtCore/QtGlobal>
#include <QtNetwork/QLocalSocket>

#ifndef QAPPLICATION_CLASS
#define QAPPLICATION_CLASS QCoreApplication
#endif

#include QT_STRINGIFY(QAPPLICATION_CLASS)

class SingleApplicationPrivate;

/**
 * @brief Handles multiple instances of the same
 * Application
 * @see QCoreApplication
 */
class SingleApplication : public QAPPLICATION_CLASS {
  Q_OBJECT

  using app_t = QAPPLICATION_CLASS;

public:
  /**
   * @brief Mode of operation of `SingleApplication`.
   * Whether the block should be user-wide or system-wide and whether the
   * primary instance should be notified when a secondary instance had been
   * started.
   * @note Operating system can restrict the shared memory blocks to the same
   * user, in which case the User/System modes will have no effect and the
   * block will be user wide.
   */
  enum Mode {
    /** The `SingleApplication` block should apply user wide
     * (this adds user specific data to the key used for the shared memory and
     * server name)
     * */
    User = 1 << 0,
    /**
     * The `SingleApplication` block applies system-wide.
     */
    System = 1 << 1,
    /**
     * Whether to trigger `instanceStarted()` even whenever secondary instances
     * are started
     */
    SecondaryNotification = 1 << 2,
    /**
     * Excludes the application version from the server name (and memory block)
     * hash
     */
    ExcludeAppVersion = 1 << 3,
    /**
     * Excludes the application path from the server name (and memory block)
     * hash
     */
    ExcludeAppPath = 1 << 4
  };
  Q_DECLARE_FLAGS(Options, Mode)

  /**
   * @brief Intitializes a `SingleApplication` instance with argc command line
   * arguments in argv
   * @arg argc - Number of arguments in argv
   * @arg argv - Supplied command line arguments
   * @arg allowSecondary - Whether to start the instance as secondary
   * if there is already a primary instance.
   * @arg mode - Whether for the `SingleApplication` block to be applied
   * User wide or System wide.
   * @arg timeout - Timeout to wait in milliseconds.
   * @note argc and argv may be changed as Qt removes arguments that it
   * recognizes
   * @note `Mode::SecondaryNotification` only works if set on both the primary
   * instance and the secondary instance.
   * @note The timeout is just a hint for the maximum time of blocking
   * operations. It does not guarantee that the `SingleApplication`
   * initialisation will be completed in given time, though is a good hint.
   * Usually 4*timeout would be the worst case (fail) scenario.
   * @see See the corresponding `QAPPLICATION_CLASS` constructor for reference
   */
  explicit SingleApplication(int &argc, char *argv[],
                             bool allowSecondary = false,
                             Options options = Mode::User, int timeout = 1000,
                             const QString &userData = {});
  ~SingleApplication() override;

  /**
   * @brief Checks if the instance is primary instance
   * @returns `true` if the instance is primary
   */
  bool isPrimary() const;

  /**
   * @brief Checks if the instance is a secondary instance
   * @returns `true` if the instance is secondary
   */
  bool isSecondary() const;

  /**
   * @brief Returns a unique identifier for the current instance
   * @returns instance id
   */
  quint32 instanceId() const;

  /**
   * @brief Returns the process ID (PID) of the primary instance
   * @returns pid
   */
  qint64 primaryPid() const;

  /**
   * @brief Returns the username of the user running the primary instance
   * @returns user name
   */
  QString primaryUser() const;

  /**
   * @brief Returns the username of the current user
   * @returns user name
   */
  QString currentUser() const;

  /**
   * @brief Mode of operation of sendMessage.
   */
  enum SendMode {
    NonBlocking, /** Do not wait for the primary instance termination and return
                    immediately */
    BlockUntilPrimaryExit, /** Wait until the primary instance is terminated */
  };

  /**
   * @brief Sends a message to the primary instance
   * @param message data to send
   * @param timeout timeout for connecting
   * @param sendMode - Mode of operation
   * @returns `true` on success
   * @note sendMessage() will return false if invoked from the primary instance
   */
  bool sendMessage(const QByteArray &message, int timeout = 100,
                   SendMode sendMode = NonBlocking);

  /**
   * @brief Get the set user data.
   * @returns user data
   */
  QStringList userData() const;

Q_SIGNALS:
  /**
   * @brief Triggered whenever a new instance had been started,
   * except for secondary instances if the `Mode::SecondaryNotification` flag is
   * not specified
   */
  void instanceStarted();

  /**
   * @brief Triggered whenever there is a message received from a secondary
   * instance
   */
  void receivedMessage(quint32 instanceId, QByteArray message);

private:
  SingleApplicationPrivate *d_ptr;
  Q_DECLARE_PRIVATE(SingleApplication)
  void abortSafely();
};

Q_DECLARE_OPERATORS_FOR_FLAGS(SingleApplication::Options)

#endif // SINGLE_APPLICATION_H
